Electrical machine



DeC- 15 1931. T. NlLssoN-STIG 1,836,882

ELECTRICAL MACHINE Filed Aug. 5, 1929 d zg [HHM A will Patented Dec. l5,1931 UNITE-asians rATeNr omer.

TORSTEN NIILSSON-STIG',Y OF UMEA, SWEDEN ELECTRICAL KACHINE ppucatiuumed august s, 1929, serial No. season, aud in sweden August 16, 192s.

The present invention has for its Object to provide electrical machines,generators, motors or converters with appreciably reduced iron losses,whereby the efficiency may in cer- 8 tain cases be improved upon.

The characteristic feature of the invention resides in that the armaturewindings are inserted into a special former or frame of elec tricallyand magnetically insulating mate- !0 rial, such as synthetic resins asakelite, pressboard, presswood, paper, mica prepared or treated withsynthetic resins, steatite and materials with equal properties of theproper mechanical strength, said former, or

15 frame being placed between the magnetically active parts of themachine. Thus, the air gap will be increased, and in consequence theretothe machine requires more powerful excitation. The constructionwill,therefore,

90 'show to the best advantage in such types of machines where the ironlosses are great in relation to the losses of excitation. This is aboveall the case in alternating current machines for a higher periodicitythan that of the common systems of .power transmission.

The invention will be more clearly described with relationvto theannexed drawings, in which Figs. l to 3 show by way of example anddiagrammatically parts of an electric machine according to differentforms of embodiment. Fig. 4 1s an end view of a machine having a windingvarrangement according to the embodiment shown in Fig. 3.

y Referring to the figures, A and B here designate the magneticallyvactive parts of the machine. C is-'a former or frame of insulatingsolid material, and D and E are the armature windings.

v As mentioned hereinbefore, this machine construction is particularlyadvantageous in machines for rather high alternating currentfrequencies.

The'armature conductors of the high frequency windings may be sodisposed in their frame orformer as to bebrought nearer to that part ofthe machine which is in movement relatively to the said winding' duringoperation, and at any rate, in regard to the A strength of the materialof the frame, as'near as possible 'to said part ofthe machine. Most highfrequency machines'are of the so-called indu'ctor type, where the rotoris generally provided with slots and teeth in the iron, wherebypulsations are caused in the ma netic field. These pulsations generatetfie high frequency in a suitably adapted armature winding. It is thenobvious that the differences in density of the magnetic field arereduced with the distance from the teeth and the slots, by reason ofwhich it is of the greatest importance for the output of the machinethat the armature winding is brought nearer to that part of the machine,which is provided with teeth and slots and which is in movementrelatively to the winding during operation, than to the othermagnetically active parts of the machine.

Moreover, the space between the iron masses of the stator and the rotorof the machine, which is the same as itsV magnetically active parts,should be made so larve that the high frequency pulsations in t emagnetic field are equalized as far as possible/when the magnetic fieldhas moved over the intervening space or the air-gap. It is also ofimportance that that part of the machine, which during operation is notin motion relatively to the armature winding, while being magneticallyoperative, has no slots adjacent to the air-gap or the intermediatespace between the rotor and the stator, in order that the high frequentmagnetic changes of density in the iron may become as smal as possible.

Figs. 2 and 3 of the drawings show how the high frequency winding D isdisposed in its frame C connected to the stator A, in such a mannerhowever that the winding is brought nearer to the rotor B provided withslots and teeth. The width of the air-gap is also disclosed, and itlwill be seen that the stator has noslots.

High frequency machines may also be made of another type where the mainmagnetic field is made with pronounced poles, as shown in Fig. 3, theexternal portions of the main poles being provided with slots and teeethso adapted that the high frequency pulsa-tions in the magnetic field allaround the circumference co-operate toward genion erating a highfrequency E. M. F. in the armature winding D. This is effected in suchmanner that the slots of the magnet winding M at the external portionsof the rotor B are given a Width corresponding to an even number ofslots and teeth, as shown in Fig. 3 by ldotted lines In this way, theteeth under north pole magnetization are caused to cooperate with theslots under south pole magnetization, and vice Versa.

A high frequency machine withl prof nounced poles may also be -providedwith an additional armature winding for low i frequency or directcurrent, intended to drive the machine in co-operation with the mainfield. This winding, which is designated by E in Fig. 3, should also bedisposed in a frameV or former of insulating solid material between themagnetically active parts of the machine, or, saidwin'ding may bedisposed in the same frame C as the high frequency winding D. A.

According to the invention, electrical machines may also be devised asindicated in Fig. l that is'to say, with the armature windings D intheir frame C free from the magnetically active parts A andB, whichparts are in this case in motion relatively to the armature windingsduring operation, the main pole pitch aswell yas the pitch of the slotsand teeth having then to be the same in AV and B. d d

In high frequency machines, all conductors of the armature windingsshould consist.

lof finely divided enamelled vcopper'wires,in

order to reduce the copper losses as far as possible.

All rotor slots should be filled outwardly with bronze wedges, for thepurpose of re-j ducing the air friction and of retaining the magnetwindings or the like. Y

Preferably the frames or formers intended; to carry the armaturewindings vfirst be provided with slots for .the conductors and may beassembled as a unit, whereupon the windings are drawn into the slots. A

`What l claim is i Y Y 1. A rotary electrical machine, comprising.magnetically active iron parts rotatable rela#y tively to each other, arigid frame or former of electrically and magnetically insulating:

material located between Ysaid magnetically active iron parts, andgenerating windings,

inserted in said insulating frame or former.`

Imagnetically insulating material located be-'L tween said magneticallyactive iron parts, and

generating windings inserted in said insulat" ing frame or former, saidgenerating winding Y being so disposed that'the centres of gravity ofthe sections of its conductors will be situ- 2. A rotary electricalmachine, adapted for f generating high frequence alternating cur r-ent,comprising magnetically active iron.

tween saidmagnetically active ironparts,

and generating windings inserted in said insulating frame or former, oneof said-magnetically active iron parts havingslots and teeth at itscircumference, the gap between said iron parts being so great that thedierences in the magnetic flux caused by said slots and teeth areequalized or nearlyequali'zed,when the magnetic flux has traversed saidgap.

4. A rotary electrical machine, adapted for generating highfrequencealternating current, comprising magnetically active iron partsrotatable relatively to Veach other, a rigid frame or former ofVelectrically and magnetically insulating 'material located between saidmagnetically Vactive iron parts, and generating windings inserted insaid insulating frameor former, that part `of the said magneticallyactive iron parts,'which during operation is stationary relatively tosaid generating winding/having no slots,l

of electrically and magnetically insulating material located betweensaidmagnetically active ironk parts, and generating windingsV insertedin said insulating frame or former, that part ofv said magneticallyactive iron parts, whichV form the main magnetic held, being equippedwith pronounced pole pieces,

.` the external portions of said pole pieces being provided with slotsand teeth causing such differences in 'the'magnetic flux asto inducehigh frequency alternating E. M. F., said slots and teeth being sodisposed that the teeth under north pole magnetization co-operate withthe slots under south pole magnetization and vice versa.

6. A rotary .electrical'machine` according to claim 5, characterized-'bythe factrthat there is inserted. in addition tothe winding forgenerating high frequency alternating current, in thatv part of themachine which carries the said winding, a second winding for generatinglow frequency alternating current or directcnrrent intended to drivethemachineV in 4cooperation with the main magnetic field. A

lntestimony whereof I affix my signature.

ToRsTEN NiLssoN-'sTia

